1. Field of the Invention
The present invention relates to a dispersion-type EL device used for an input unit etc. of various types of electronic equipment and an illuminated switch unit using the same.
2. Background Art
Hereinafter, a conventional dispersion-type EL device (hereinafter referred to as “EL device”) and an illuminated switch unit (hereinafter referred to as “switch unit”) using the same are described with reference to FIGS. 13 and 14.
FIG. 13 is a sectional view showing a conventional EL device. EL device 101 includes insulating substrate 102, transparent electrode layer 103, luminescent layer 104, dielectric layer 105, back electrode layer 106, and insulating layer 107. Insulating substrate 102 is made of a transparent resin film having a thickness of about 100 μm. On the back surface of insulating substrate 102, transparent electrode layer 103 is formed by a thin film formation technique such as a sputtering method. On transparent electrode layer 103, luminescent layer 104, dielectric layer 105, back electrode layer 106, and insulating layer 107 are sequentially laminated. Note here that the dimensions in the thickness direction in FIGS. 13 and 14 are enlarged relative to scale.
In EL device 101, when ac voltage or dc pulse voltage is applied between transparent electrode layer 103 and back electrode layer 106 by a driver circuit (not shown), a fluorescent substance in luminescent layer 104 emits light. Light emitted from luminescent layer 104 passes through the side of insulating substrate 102 that is a light-emitting surface side of EL device 101, and is illuminated.
FIG. 14 is a sectional view showing a conventional switch unit using EL device 101.
As shown in FIG. 14, switch unit 108 has membrane switch portion 114. Membrane switch portion 114 has a configuration in which spacer 113 is adhesively attached between upper insulating plate 109 (hereinafter referred to as “plate 109”) and lower insulating plate 111 (hereinafter referred to as “plate 111”). Plate 109 is made of a resin film having a thickness of about 100 μm. Movable contact 110 (hereinafter referred to as “contact 110”) is printed on the lower surface of plate 109. Plate 111 is made of a resin film. Stationary contact 112 (hereinafter referred to as “contact 112”) is printed on the upper surface of plate 111. Spacer 113 is adhesively attached between plate 109 and plate 111 so that contact 110 and contact 112 face each other with predetermined space therebetween. Contacts 110 and 112, which face each other, constitute switch portion 119.
EL device 101 including insulating substrate 102 having a driver circuit that is independent from that of membrane switch portion 114, is located on membrane switch portion 114. EL device 101 has a total thickness of about 0.3 mm. Furthermore, in an upper part of EL device 101, spacer 118 and surface sheet 117 are sequentially disposed. Push buttons 115, which are located above individual switch portions 119, are attached to a lower surface of surface sheet 117 with adhesive member 116. A lower end portion of push button 115 is brought into contact with EL device 101. Thus, switch unit 108 is configured.
Push button 115 is depressed by applying pressure (for example, with a finger, a pen, etc.) through surface sheet 117. When push button 115 presses EL device 101, the pressed portion of EL device 101 is partially flexed and plate 109 disposed at a lower side of EL device 101 is also partially flexed. Thus, contact 110 is depressed, so that a lower surface of contact 110 is brought into contact with an upper surface of contact 112. Then, contact 110 and contact 112 are electrically connected to each other, and switch portion 119 is turned on.
When the operated power to surface sheet 117 is removed, plate 109 and EL device 101 return to the original states by their own restoring forces, so that switch portion 119 is turned off again as shown in FIG. 14.
Note here that devices similar to EL device 101 and switch unit 108 are disclosed in, for example, Japanese Patent Unexamined Publication No. H10-106754.